Changed the way keys are processed.

Changed the way keys are processed.

Until today vimb mapped two-part keybindings to commands. This patch changed
this paradigm into a more vi like way. The commands are separated into normal
mode commands that mainly consists of a single char and ex commands that can
by typed into the inputbox like ':open'. This change allows us to adapt also
the way keypresses and mapping are handled. Now every keypress is converted
into a unsigned char and collected into a typeahead queue. The mappings are
applied on the queue. So now we can use also long keymaps and run multiple
commands for different modes with them like ':nmap abcdef :set
scripts!<CR>:open search query<CR>50G'.